Gas turbine engines produce power by extracting energy from a flow of hot gas produced by combustion of fuel in a stream of compressed air. In general, turbine engines have an upstream air compressor coupled to a downstream turbine with a combustion chamber (“combustor”) in between. Energy is released when a mixture of compressed air and fuel is burned in the combustor. The resulting hot gases are directed over blades of the turbine to spin the turbine and produce mechanical power. In a typical turbine engine, one or more fuel injectors direct some type of liquid or gaseous hydrocarbon fuel (such, diesel fuel or natural gas) into the combustor for combustion. This fuel mixes with compressed air (from the air compressor) in the fuel injector, and flow to the combustor for combustion. Combustion of the fuel in the combustor can create temperatures exceeding 2000° F. (1093.3° C.). These high temperatures in the vicinity of the fuel injector increase the temperature of the fuel injector during operation of the turbine engine.
In fuel injectors, fuel lines and fuel galleries are used to direct the fuel to the combustor. The high temperatures of the fuel injector during operation may lead to coking of liquid fuel in these lines and galleries. Over time, this coke deposit in the lines and galleries can lead to flow restrictions that adversely affect the operation of the gas turbine engine. In some fuel injectors, insulating cavities or shrouds may be disposed around fuel lines or galleries that are susceptible to coking.